Bearing cap for electric motor

ABSTRACT

A unit bearing motor is provided with a vented bearing cap which allows air to escape to the atmosphere as the cap is telescoped into a bearing housing.

United States Patent 1 Anderson, Jr.

1 1 July 31, 1973 1 BEARING CAP FOR ELECTRIC MOTOR [75] Inventor: GordonR. Anderson, Jr., Roscoe, .111.

[73] Assignee: Airtrol Corporation, Rockton, 111. [22] Filed: Aug. 23,1972 [21] Appl. No.: 283,190

[52] US. Cl 310/90, 308/132, 308/134.1,

[51] Int. Cl. H0211 5/16 [58] Field of Search 310/90, 67, 72; 308/132,134.1, 163; 184/64, 102

[56] References Cited UNITED STATES PATENTS 3,626,221 12/1971 Anderson310/90 3,663,849 5/1972 Hoeb 310/163 3,387,153 6/1968 Grad 310/903,513,339 5/1970 Harris 310/90 Primary ExaminerR. Skudy Attorney-C.Frederick Leydig, Michael C. Payden et a1.

[57] ABSTRACT A unit bearing motor is provided with a vented bearing capwhich allows air to escape to the atmosphere as the cap is telescopedinto a bearing housing.

9 Claims, 8 Drawing Figures BACKGROUND OF THE INVENTION This inventionrelates to an electric motor and, more particularly, to an electricmotor of the type having a pair of axially spaced shaft bearings whichare telescoped into a bearing housing carried by a rotor and whichrotate on a stationary shaft projecting cantilever fashion from a statorassembly. The bearings are made of porous material and are adapted to bepermanently lubricated by an oil impregnated liner telescoped into thebearing housing and over the shaft and sandwiched between the opposinginboard faces of the bearings. A motor of this general type is disclosedin Anderson et al. U.S. Pat. No. 3,626,221.

In the present motor, the bearings and the bearing housing arecaptivated axially on the shaft by a retaining ring fastened to theouter end of the shaft and by a thrust disc located to abut the end ofthe shaft. The thrust disc is retained within a bearing cap adapted tobe assembled telescopically with the outer end of the bearing housing.As a result of the telescopic fit between the bearing cap and thebearing housing, the retaining ring is disposed within a chamber definedbetween the thrust disc and the outer bearing.

SUMMARY OF THE INVENTION The general aim of the present invention is toavoid the formation of a pressurizedair cushion in the cham-' ber duringtelescopic assembly of the bearing housing and the bearing cap andpreferably to maintain the air in the chamber at atmsopheric pressureduring the service life of the motor. By eliminating the air cushion andkeeping the chamber at atmospheric pressure, the rotor is allowed to runat its magnetic center to reduce endwise thrusting of the rotor againstthe retaining ring and thereby avoid excessive noise and end bump whileat the same time reducing the frictional drag on the rotor.

A more detailed object is to achieve the foregoing by venting thechamber to the atmosphere through the bearing cap so that air can escapefrom the chamber as the cap is assembled telescopically with the bearinghousing.

The invention also resides in the unique manner of venting the chamberand restricting the escape of lubricating oil from the vented chamber.

These and otherobjects and advantages of the invention will become moreapparent from the following detailed description when taken inconjunction with the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS bodiment of a unique bearing capconstructed in accor- I dance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED I EMBODIMENTS As shown in thedrawings for purposes of illustration, the invention is embodied in ashaded-pole motor 10 generally comprising a cylindrical rotor 11journaled for rotation on a cantilevered shaft 13 rigid with andprojecting outwardly from the frame bracket 14 of a stator assembly. Theframe bracket supports a field core 16 which is formed by sets ofstacked laminations secured to the bracket by pins 18 and defining acylindrical opening 20 within which the rotor is disposed. Wrappedaround a portion of the stator is a primary winding 22 adapted forconnection to a source of alternating current voltage, and placed inselected positions in the stator are the usual shading coils 24 and 26.

The rotor l 1 includes a central tubular bearing housing 28 (FIG. 2)press-fitted into a series of stacked sheet metal stampings which coactwith a plurality of conductors (not shown) to form the secondary windingof the motor. Alternatively, the housing 28 may be formed as an integralpart of the secondary winding of the motor. As shown in FIG. 2, thehousing is telescoped onto the shaft 13 and is supported thereon byinner and outer axially spaced bearings 38 and 40 which are press-fittedinto the housing and received rotatably on the shaft with a running fitso that the rotor 11 thus can turn freely on the shaft.

Formed between the bearings 38 and 40 is a chamber 48 (FIG. 2) adaptedto hold a quantity of oil for lubricating the bearings during the entireservice life of the motor. A tubular liner 50 of felt or other absorbentmaterial for conducting oil to the bearings is disposed within thechamber with its ends contacting the inboard faces of the bearings. Theliner is pressed into the bear-' ing housing 28 and is telescopedloosely over the shaft 13 so as to leave the rotor 11 free to turnwithout being retarded as a result of frictional contact of the linerwith the shaft. The bearings are made of sintered metal and are somewhatporous so that oil delivered to the bearings by the liner may work itsway through the bearings to lubricate the shaft between the latter andthe bearings and thus reduce wear and running friction. Slots 51 areformed in the bearings and restrict the escape of oil past the bearingsin the manner disclosed in my copending application Ser. No. 241,703,16, 1972. y

Located adjacent the outboard face of the inner bearing 38 and pressedinto the housing 28 is a felt ring 53 (FIG. 2) which abuts an annularflange 54 extending around the inner end of the housing, the flangeserving to captivate the inner bearing within the housing. A

face of the. outer bearing 40 while a metal snap ring 56 is fastened totheouter end portion of the shaft 13 to captivate the rotor I 1 againstoutward movement off of the shaft. Telescoped loosely over the shaft andsandwiched between the felt ring 55 and the snap ring 56 is a thrustwasher 57 which is made of nylon or the like to reduce friction betweenthe felt ring and the snap ring.

As shown in FIG. 2, a cylindrical bearing cap 60 is telescoped into theouter end portion of the housing 28 with a press fit and carries anarbor 63 adapted to sup port a device such as the hub 65 of a fan blade(not shown) which is to be driven by the motor 10. In this filed Apr.

instance, the arbor is formed integrally with the bearing cap.

The inner end portion of the bearing cap 60 is formed with a cylindricalopening 67 having a conical end wall 69. Disposed in the opening andbacked by the wall 69 is a nylon thrust disc 70 which abuts the outerend of the shaft 13 to limit movement of the rotor 11 inwardly along theshaft. As shown in FIG. 2, a chamber 71 is de-' fined between the thrustdisc 70 and the felt ring 55 and such chamber contains the snap ring 56and the thrust washer 57.

In assembling the motor 10, the felt ring 53, the inner bearing 38, theoil liner 50, the outer bearing 40 and the felt ring 55 are all pressedinto the bearing housing 28 in stacked relation and then the entireassembly is telescoped onto the shaft 13. After the thrust washer 57 andthe snap ring 56 have been installed on the shaft the bearing cap 60(with the thrust disc 70 therein) is press-fitted into the outer end ofthe bearing housing. As an incident to pressing the cap into thehousing, the air in the chamber 71 becomes compressed and tends to forma pressurized air cushion within the chamber since the cap acts like apiston as it is slid into the housmg.

According to the present invention, provision is made of a passage 75(FIG. 2) which vents the chamber 71 to the atmosphere as the bearing cap60 is telescoped into the bearing housing 28 so that the air beingcompressed in the chamber may escape to. avoid the formation of apressurized air cushion in the chamber. In the preferred embodiment, thepassage also vents the chamber continuously during the life of the motorand thus changesin atmospheric pressure will not cause a build up ofpressure or vacuum within the chamber. As a result of venting thechamber, the latter is free of any air cushion which otherwise wouldcause the rotor 11 to run off of its magnetic center and thrustoutwardly against the snap ring 56. Excessive bumping of the rotoragainst the snap ring thus is avoided so as to reduce noise and decreasefriction during operation of the motor.

In the preferred embodiment shown in FIG. 2, the passage 75 extendsaxially through the center of the arbor 63 and the end cap 60 andcommunicates with the chamber 71 through a small hole 77 formed throughthe center of the thrust disc .70. Preferably, the passage tapersgradually upon progressing outwardly from the conical wall 69 to theouter end of the arbor. To restrict the escape of oil through thepassage, a seal in the form of a felt disc 80 is sandwiched between thewall 69 and the thrust disc 70 and is disposed in face-toface relationwith the outer face of the thrust discto cover the hole 77. Whilerestricting the escape of oil through the hole 77, the felt disc 80 issufficiently porous to allow air to flow through the hole from thechamber 71 and thence into the passage 75.

.With the foregoing arrangement, air in the chamber 71 can escapethrough the hole 77 and the passage 75 when the end cap 60 ispress-fitted into the bearing housing 28 during assembly of the motor10. In addition, the chamber is vented continuously during the servicelife of the motor so that the air in the chamber remains at atmosphericpressure at all times. When the motor is running, centrifugal forcespins any free oil in the chamber toward the inner circumferential wallof the opening 67 in the end cap and prevents leakage of such oilthrough the hole 77 and the passage 75. When the motor is not operating,the felt disc 80 restricts the escape of oil through the hole and thepassage. Because the passage is tapered, any residual free oil whichdoes escape into the passage is pumped back into the felt disc 80 bycentrifugal force when the motor is initially started up.

FIG. 3 shows an alternative form which the thrust disc may take, thedisc being indicated by the reference numeral 70A. In this case, twodiametrically spaced notches are formed in the peripheral edge of thedisc to establish communication between the chamber 71 and the passage75. In the embodiment shown in FIG. 4, the passage 758 through thebearing cap 608 is cylindrical and is closed off by a cylindrical feltplug 86 telescoped into the passage, the plug serving the same purposeas the felt disc 80. FIG. 5 shows a bearing cap 60C with a slantedpassage 75C which opens out of the end of the body of the cap ratherthan extending through the arbor 63C.

Another version of the invention is shown in FIGS. 6 and 7. In thisinstance, the arbor 63D is formedseparately of the main body of thebearing cap 60D and is press fitted into a hole 90 extending through thebody. Diametrically spaced groove 91 are formed in the wall of the hole90 to establish communication between the chamber 71 and the outsideatmosphere and thereby vent the chamber. In place of the grooves 91, oneor more grooves could be formed in the outersurface of the arbor 63D. I1

In the embodiment shown in FIG. 8, a vent passage 75E extends radiallythrough the main body of the bearing cap 60E. As the bearing cap istelescoped into the housing ,28, the passage 75E initially vents thechamber 71 but then is covered up when the bearing cap is fully seated.With this arrangement, there is no danger at all of oil escaping throughthe passage but the chamber is vented only during assembly and notduring continuous operation of the motor.

I claim as my invention:

1. An electric motor having a stator assembly with a stationary shaftcantilevered thereon and projecting outwardly therefrom, a rotor havinga centrally located tubular bearing housing telescoped over said shaft,inner and outer axially spaced sleeve bearings of porous material fixedwithin said housing and rotatable on said shaft, an oil-impregnatedtubular liner telscoped into said housing and over said shaft andsandwiched between the inboard faces of said bearings, a retaining ringfastened to the outer end portion of said shaft to captivate saidhousing and said bearings on said shaft, and a bearing cap telescopedinto the outer end portion of said housing with a press fit and closingoff the outer end portion of the housing, said bearing cap having anopening in its inner end for receiving the outerend portion of saidshaft, the improvement in said motor comprising, a thrust disc disposedwithin said opening between the outer wall thereof and the outer end ofsaid shaft and defining the outer wall of a chamber which encloses saidretaining ring, a hole extending through said thrust disc andcommunicating with said chamber, a passage formed in said bearing capand communicating with said hole, said passage also communicating withthe atmosphere to vent said chamber to the atmosphere and therebyprevent the formation of an air cushion in said chamber, and anabsorbent seal of porous material disposed in said opening between saidthrust disc and said passage and covering said hole to restrict theescape of oil through the hole and into the passage 2. An electric motoras defined in claim 1 in which said pasage is centered relative to theaxis of said shaft and opens out of the outer end of said bearing cap.

3. An electric motor as defined in claim 2 in which said passage tapersgradually upon progressing toward the outer end of said bearing cap.

4. An electric motor as defined in claim 2 in which said seal comprisesa felt plug telescoped into said passage and located with its inner endabutting the outer surface of said thrust disc and covering said hole.

5. An electric motor as defined in claim 1 in which said seal comprisesa felt disc disposed in face-to-face relation with the outer surface ofsaid thrust disc.

6. An electric motor having a stator assembly with a stationary shaftcantilevered thereon and projecting outwardly therefrom, a rotor havinga centrally located tubular housing member telescoped over said shaft,inner and outer axially spaced bearings fixed within said housing androtatable on said shaft, a retaining ring fastened to the outer endportion of said shaft to hold said housing and said bearings on theshaft, and a cap member assembled telescopically with the outer endportion of said housing with a press fit and closing off the outer endportion of the housing whereby said retaining ring is disposed within achamber defined in said housing between said cap and said outer bearing,the improvement in said motor comprising, passage means formed in one ofsaid members and communicating with said chamber, said passage meansalso communicating with the atmosphere at least during telescopicassembly of said cap member with said bearing member thereby to ventsaid chamber to the atmosphere and avoid the formation of an air cushionin said chamber.

7. An electric motor as defined in claim 6 in which said cap istelescoped into said housing, said'passage means being formed in saidcap.

8. An electric motor as defined in claim 7 in which said passage meansestablish communication between said chamber and the atmosphere onlyduring telescopic assembly of said cap into said housing, the outer end.of said passage means being closed off by said housing after telescopicassembly of said cap into said housing.

9. An electric motor as defined in claim 7 in which said passage meansestablish communication between said chamber and the atmosphere bothduring and after telescopic assembly of said cap into said housing, theouter end of said passage means remaining open to the atmosphere aftertelescopic assembly of said cap into said housing.

1. An electric motor having a stator assembly with a stationary shaftcantilevered thereon and projecting outwardly therefrom, a rotor havinga centrally located tubular bearing housing telescoped over said shaft,inner and outer axially spaced sleeve bearings of porous material fixedwithin said housing and rotatable on said shaft, an oil-impregnatedtubular liner telscoped into said housing and over said shaft andsandwiched between the inboard faces of said bearings, a retaining ringfastened to the outer end portion of said shaft to captivate saidhousing and said bearings on said shaft, and a bearing cap telescopedinto the outer end portion of said housing with a press fit and closingoff the outer end portion of the housing, said bearing cap having anopening in its inner end for receiving the outer end portion of saidshaft, the improvement in said motor comprising, a thrust disc disposedwithin said opening between the outer wall thereof and the outer end ofsaid shaft and defining the outer wall of a chamber which encloses saidretaining ring, a hole extending through said thrust disc andcommunicating with said chamber, a passage formed in said bearing capand communicating with said hole, said passage also communicating withthe atmosphere to vent said chamber to the atmosphere and therebyprevent the formation of an air cushion in said chamber, and anabsorbent seal of porous material disposed in said opening between saidthrust disc and said passage and covering said hole to restrict theescape of oil through the hole and into the passage
 2. An electric motoras defined in claim 1 in which said pasage is centered relative to theaxis of said shaft and opens out of the outer end of said bearing cap.3. An electric motor as defined in claim 2 in which said passage tapersgradually upon progressing toward the outer end of said bearing cap. 4.An electric motor as defined in claim 2 in which said seal comprises afelt plug telescoped into said passage and located with its inner endabutting the outer surface of said thrust disc and covering said hole.5. An electric motor as defined in claim 1 in which said seal comprisesa felt disc disposed in face-to-face relation with the outer surface ofsaid thrust disc.
 6. An electric motor having a stator assembly with astationary shaft cantilevered thereon and projecting outwardlytherefrom, a rotor having a centrally located tubular housing membertelescoped over said shaft, inner and outer axially spaced bearingsfixed within said housing and rotatable on said shaft, a retaining ringfastened to the outer end portion of said shaft to hold said housing andsaid bearings on the shaft, and a cap member assembled telescopicallywith the outer end portion of said housing with a press fit and closingoff the outer end portion of the housing whereby said retaining ring isdisposed within a chamber defined in said housing between said cap andsaid outer bearing, the improvement in said motor comprising, passagemeans formed in one of said members and communicating with said chamber,said passage means also communicating with the atmosphere at leastduring telescopic assembly of said cap member with said bearing memberthereby to vent said chamber to the atmosphere and avoid the formationof an air cushion in said chamber.
 7. An electric motor as defined inclaim 6 in which said cap is telescoped into said housing, said passagemeans being formed in said cap.
 8. An electric motor as defined in claim7 in which said passage means establish communication between saidchamber and the atmosphere only during telescopic assembly of said capinto said housing, the outer end of said passage means being closed offby said housing after telescopic assembly of said cap into said housing.9. An electric motor as defined in claim 7 in which said passage meansestablish communication between said chamber and the atmosphere bothduring and after telescopic assembly of said cap into said housing, theouter end of said passage means remaining open to the atmosphere aftertelescopic assembly of said cap into said housing.